Hiya, this is my field (Photography) so I think I’ll toss my 2=A2 in. =
A
gray card will work, but they’re usually kinda small, and rigid.
Photography stores usually carry a line of backdrop cloths, and
display items for shooting small objects. In my experience, I find
these to be an overpriced waste, and instead head to the fabric
section of Wal-Mart, or any fabric store, and get a few yards of
various color velvet. Velvet is not cheap, but cheaper than the photo
store stuff. Also, velvet has a property that make is ideally suited
for photography in that you don’t get glare from it, just a nice
smooth color. I know Wal-Mart will usually have black, red, and dark
blue. They can also usually get velvet in white and pastel colors.
Hope that helps, and btw, check out the Cloud Dome product, I don’t
own one, but I’ve used one, and they do work well, especially on
colored stones.